Interferometric distillation and determination of unknown two-qubit entanglement

TL;DR

This paper presents a practical interferometric method for distilling and quantifying entanglement in unknown two-qubit states, using local filtering and interference visibility measurements, offering an alternative to full state tomography.

Contribution

It introduces a novel interferometric scheme that simultaneously distills and measures entanglement without requiring complete state reconstruction.

Findings

Effective entanglement distillation achieved through local filtering.

Concurrence determined directly from interference visibilities.

Scheme compares favorably with full state tomography in efficiency.

Abstract

We propose a scheme for both distilling and quantifying entanglement, applicable to individual copies of an arbitrary unknown two-qubit state. It is realized in a usual two-qubit interferometry with local filtering. Proper filtering operation for the maximal distillation of the state is achieved, by erasing single-qubit interference, and then the concurrence of the state is determined directly from the visibilities of two-qubit interference. We compare the scheme with full state tomography.